1. Filed of the invention
The present invention relates to a device to vibrate the body of the subject at a prescribed frequency to effect vibration therapy.
2. Description of the Prior Art
As to conventional device, Japanese Patent Laid-Open No. 209,355/83 discloses a device wherein a vibratory plate to be placed on the body of the subject is coupled through a closed gas space with a loudspeaker, while its voice coil is connected with a variable frequency oscillator through an amplifier. The device has the advantages that its vibration frequency can be conveniently set to the most effective level for the particular subject; and that the gas used as the vibration-transmitting media transmits the vibration over a relatively large body area of the subject.
The device, however, has the drawback that, when the closed gas space is extended with a flexible hose having a relatively small diameter, it requires a relatively high power to attain a prescribed sound pressure on the vibratory plate because gases are generally low in vibration transmittability. This unnecessarily enlarges both vibratory plate and amplifier to raise the production cost of the device.
The present inventor proposed in Japan Patent Application No. 72,435/86 that the closed gas space is compressed to increase its vibration transmittability in order to decrease the loss on vibration energy.
This proposal still has the drawbacks that the compression hardens the vibratory member to decrease the balance feeling when the subject lies thereon, as well as that it unfavorably requires a high airtight structure.